I could understand how some may feel that things such as the full-auto ban of '86 does constitute a form of tyranny, (gov unilaterally imposing changes upon the people, even tho they may have no legal right to do so).

You could also argue that since the populace had access to full-auto weapons in 1985, the ideals of the 2nd amendment were being more closely upheld then, compared to even a year later.

What I cant understand, is how you could then state that upholding the 2nd amendment provides a deterrent against such tyranny?
Sure, one of the theoretical intents of the 2nd amend was just that, but observation shows us there is a big gap between theory and actual practice.

I love cars. If there was a constitutional amendment which guaranteed my right to own & drive a car, then I'd be upset if laws were passed to make it harder for me to do that. Maybe they start by saying I cant own more than 300 HP. Later, they start talking about limiting the max size of my gas tank to 3 gallons, so I cant drive far. I'd want to fight to stop such changes, of course, since I'm not smashing into people with my car. I could stand there with all the righteous indignation in the world and scream "I'm not the problem !". And I'd be right; but it wouldn't help.

If I observed that the car amendment failed miserably to stop the 300HP limit then, I'd put little hope in it helping with my gas tank issue today. I'd probably stop trying to draw attention to the importance of maintaining the ideals of the amendment, when practically, it appears to yield no fruit. Maybe it shouldnt be like that, but it is. Being more solution oriented, than tradition or process oriented, I'd look for other ways.

Remember, the only way they got Al Capone off the street was by nailing him for tax evasion. If the prosecutors got hung up on, "dammit, he committed murder, I should be able to punish him for THAT!", he woulda been a free man till his death. Just sayin'...